Seven (VII) Rules to Follow

Roman numerals can be tricky; however, you just need some basic knowledge working as a tech. Here are seven rules that lays a basic foundation for using Roman numerals in a pharmacy setting:

1. Roman numerals on prescriptions will not be capitalized. For example, expect to see ii instead of II to denote 2. Example: ii tabs qd po means two tablets every day by mouth.

2. A Roman numeral is capitalized when referring to a controlled drug. Example: Lyrica is a Schedule V drug. Note: if you see it written as CV or C-V, do not confuse the C as the Roman numeral for 100. In this case, C is shortened for “Control”.

3. To write one-half (½), use ss or ṡṡ.

4. Always use the biggest numeral possible. For example, you would want to denote 10 as X, not VV.

5. Always put your numerals in descending order left to right, UNLESS you are subtracting. For example, CX is 110, while XC is 90. Furthermore, it is important to note that you can only use the same numeral in order three
times so it is incorrect to use LXXXX for 90.

6. To further build on Concept #3, you cannot place more than one smaller numeral to the left of the larger one. It is appropriate to denote 19 as XIX, but to denote 18, you must follow the left to right concept and write it as XVIII.

7. Finally, when subtracting, the lesser numeral to the left cannot be less than one-tenth of the numeral from which you are subtracting. For example, you cannot use I or V to subtract from C. The number 99 is written as XCIX and 95 as XCV.

Do not worry too much about big calculations using Roman numerals. The most common places will be on a prescription for 3 or fewer pills and when listed for a control. You will not spend your days doing Roman numeral calculations.

Roman Numerals List

Roman	Arabic
I	1
II	2
III	3
IV	4
V	5
VI	6
VII	7
VIII	8
IX	9
X	10
L	50
C	100
M	1,000